Method of manufacturing curved structural elements



June 6, 1950 A. v. PEDERSEN I 2,510,602

METHOD OF MANUFACTURING CURVED STRUCTURAL ELEMENTS Original Filed Dec. 29, 1943 15 IN VEN TOR.

Qxe/ 2/. Peder-sen bUN lTED Patented June 6, i950 METHOD or MANUFACTURING CURVED STRUCTURAL ELEMENTS Axel V. Pedersen, Los Angeles.

Continuation of Application Serial No. 516,067, December 29, 1943. This application November 3, 1947, Serial N0. 783,772

. 1 r This invention-relates to a method of manufacturing laminated structural elements from wood laminations. This application is a continuation of my copending application, Serial No.

516,067,- filed December 29, 1943, now abandoned.

-I-Ieretofore in the manufacture of structural elements from wood laminations such as, for example, in the manufacture of curved chords of bowstring and other type trusses, curved arches and the likeit has been common prac- 2' Claims. (o1. 154 110)' tice to scarf the adjacent ends of adjoining lamination sections. Single scarfs have been universally employed for this purpose having such slopes that when the scarfed ends of adjoining lamination sections are glued together adequate structural strength wil1 be developed across the joint between the lamination sections. Where single scarfs are employed the customary slope :is in the neighborhood of 1 to 10 or 1 to 12 to developthe desired strength in the joint. The use of such slopes is objectionable because of the wastage of woodinvolved in forming the scarfed ends.

Another objection to the use of single scarfs on the adjacent ends of adjoining laminated sections of curved structural elementsresides in the fact that unnecessary labor and time is involved in the gluing up of the element. If the ends of the laminations have complementary single scarfs the scarfed surfaces ordinarily must be glued together to join the lamination sections in end to end relationship. After these sections are thus connected to each other the various laminations that are made up of the lamination sections are then assembled together with adhesive. applied to their side faces and bent to the desired shape allowing the glue or adhesive to dry or set while thus bent. Such a procedure involves two separate gluing operations; one in which the scarfed ends are glued together and the second wherein the laminations are bent and glued to each other.

If an attempt is made to simultaneously glue the scarfed ends to each other and to glue the lamination faces to each other the clamps of the gluing frame must be positioned opposite each of the scarfed joints due to the fact that as these scarfs are single scarfs the joints will tend to open .under the bending. As it is desirable to have the scarfed joints disposed in staggered relation throughout the structural element it is frequently difiicult and sometimes impossible to position the clamps or clamping means opposite each of the scarfed joints to hold the joint closed while the laminations are bent and the adhesive is drying or setting.

An object of the presentinvention is to provide an improved method of manufacturing structural elements of this character wherein the adjacentends of adjoining lamination sections are scarfed with oppositely directed double or multiple scarfs'capable of transmitting bending moments across the joints because of their shape. In this manner glueor other adhesive may be applied in a single gluing operation to the scarfed faces and other side faces of the lamination sections. These may then be'assembled together and bent to the desired curvature such as in aglue frame. As the double scarfs are capable of transmitting bending moments even in the absence of'any adhesive whatsoever they -will not open during the bending. Consequently,

when the adhesivev has dried or set firm-joints are established between the adjoining lamination sections and the various laminations are fastened to each other in side by side relationship.

. The: time involved in completing the gluing may accompanying drawings for an illustrative embodimentof the invention, wherein:

Fig. 1 is a top plan view of'a portion of a glue frame illustrating lamination sections in assembled relationship thereon and in the process of being bent to the desired curvature wherein the lamination'sections are allowed to remain until the adhesive has dried or set; and

Fig. 2 is an exploded view of the double scarfed adjacent ends of two adjoining lamination sections.

Referring to the accompanying drawings wherein similar reference characters designate similar parts throughout, in the construction of the structural element embodying the present invention eadjoining'lamination sections indicated at I0 and H have their adjacent-ends oppositely or double scarfed thus the section It for approximately one half of its width is scarfed upwardly as indicated at I2 toward th upper face I3 that is a continuation of the upper face of the lamination section. In a corresponding manner the other half of lamination section In is downwardly scarfed as indicated at it toward the bottom face- 3 that constitutes a continuation of the bottom surface I5 of the lamination section. The lamination section II is similarly scarfed as indicated at [6 and I! these scarfs being complementary to the corresponding scarfs l2 and I4. By scarfing the lamination sections in this manner each section has on each end thereof portions that might'b regarded as tapered tongues that ar oppositely tapered with respect to the thickness of the lamination section. The slopes of the scarfs may vary considerably but should bematernny than 1 to 1. While the slopes may begnue ss 1 to 10 or 1 to 12 I find that if the slopes' are -am proximately 1 to 6 that this is ordinarily adequate.

The slope should never be more iabflipt tl iariil tlfi ifi he: 3. When the lamination sections are thus 'scarfed they may be assembled together and even in an unglued condition it will be found that the double scarfed joints between adjoining lamination sections are capable of transmitting bendingstresses therealcross. Gonsecfueritly;in making up acurved structural element such astheelement generally designated atE on Fig. l it'is possible to-apply adhesive to-the scarfed faces-l2, I4, "5 and ll of each joint-between-adjoining lamination s'ections =and other-side faces of the lamination's. The laminationsections may then be assembled "to- {ether in a glue frame generally designated "at-=1 with the scarfed-jointsindicated at J onFig. *1 1 preferably in staggered relation to each other. The glueframe may-then-be-tightened up-tobend the laminatio'ns to -the desired curvature and to contact-with each other and the glueor other ad"- hesive that isapplied to -the=scarfed faces and to c 3 and-scope ofthe'invention'asdefined by the apthe sides or thelaminationsections allowed 1 to dry or set. When this is completed the element E may-be bodily removed from-the'glueframe and the work is completedexceptforthe application of bolts or other devices that may be required.

jacent end of adjoining lamination sections'are,

capable of transmitting bending stresses eve'ii. without the application of glue or other'fastenin'g ineansthese-joints will not-o'pen' during the bending of the lamination's on the-glue frame. -Furthermore, it is unnecessary to position clamps or other tightening devices on the=-glue frameoppm site-the joints -J It-will be appreciatedthat if the lamination sections it and H hadbeen singl scarfs thereon that the single scarf-s are incapableof transmitting bending stresses prior to the drying or -setting of the adhesive; "Consequently, if single soarfs should-be employed th scarfed surfaces wouldeither have to be :gluedtogether in' advanc'e of application to=the glue-fram 'orthe clamps-of the glue frame would have to'be positioned oppo site each scarfed joint tO-preVent'the =J'oii1tfr0m opening while thelami-nations were-being bent.

Anadditional'feature or advantage of the-present method over -the use ofsingle scarfs between adjacent ends of adjacent laminations is briefly as --follows. If single scarfed lamination sections are-first glued m end to endrelationshipand-are then bent inthe course of assembly to make a 65 curved structural 3 element not only are the lam- ;inations thus fabricated long; and 'difii cult to harm die but in the-;course of i the bend-ing the giue between thescarfed ends is prestressed-and renrains stressed in -thev completed structural-element. By means of-the present method inasmuch 'as' the glue-between the-scarred faces of adjacent-ends 56 adjacent ends of 4 of adjoining lamination sections does not dry set until after the components of the structural element have been assembled together and bent, the glue or adhesive in these joints is not prestressed.

It=will be appreciatedfrom the above described 'inethod that a new manner hf nian-ufacturing curved structural elements is provided which will khaterially reduce the gluing time normally required that the gluing of the joints and the gliiing' the'l'aniinations to each other can be ii'ffor'med"simultaneously. Furthermore, as the slopesbf the'scarfs can be reduced to as low as 1 to 6 a material saving in material is likewise 'mi's s'ible. Nb particular type of glue frame is rlji iredto'bfidfand hold the lamination sections in the desired shape. The glue frame, a portion of whichis illustrated, that is quite suitable is a gluing frame of the character disclosed in U. S.

Letters Patent' No; 2 331 972 "issued October '19,

be of unequal Width and that the number of -scarfs=may exceedwwo; -However,-the number'of scarf-s should-never =be less-than two-dueto the factthata-sirigle scarf is incapable of transmitting-bending-moments -prior 'to glu-ing and consequently will-tend to open-in the course of the bending unless otherwise prevented from so doing. 7

Various changes'm'aybe madein thedetails-of construction without departing from the spirit pended claims.

1'. The -method of making laminated curved structural *elements which =includes forming the 40 adjacent ends of adjoin'irig lamin-ation sections with complementary r pairs of opposed scarfs of slopes of not steeper than 1 to 6, applying-ad'- hesive tothe mutuallyengageabiesurfaces"of'said scarf-s. assembling the lam-inationsections to- 3v gether and bending them' to the desired curvature and allow'in'g the adhesive toset while in the bent condition; v

-2. The method of mahing.*-cnrve"dlaminated structural -'eiements whichincludes forining the oin ingl lamination sections with ccniplementa sets ofoppositely tapered tongues of slopes-bf-not steeper than i 1 to- 6; applying adhesive *to' the Y mutually engagable surfaces of said tongues and to the "sides ofthelam- 3 ination sections "assembling the lamination sec l se fishness-are of record *i'n "th aterits Oct.- 1-1 -1946 

